Where can I buy this from for cheapest? How do I install it?

for what car/motor/year?

__________________
18x8.5" B5 RS4 Reps|Nankang NS2 225/40/18|Depo Euro S4 headlights|Tint 35% Front/20% Rear|CF B+C Pillars|Stratmosphere SS|F+R D/S Rotors|Speedtuning|Custom Intake/Heatshield|Bilstein Sport Shocks/Neuspeed Race Springs|VDO Boost Guage|Samco TIP|RS4 Upper+Lower Grills|Forge Hybrid DV/BOV|Momo Shift Knob|